-"Dude, how much do you smoke? And do you like porsche cars?" -"Around a pack a day. And yeah mate, I love em!" -"Dude a pack per day costs $12. If you stop smoking, you can buy a porsche in under 10 years just from the savings from cigarettes alone..." -"Oh damn, never thought of that. Do you smoke?" -"No, never!" -"So, where is your porsche parked?"
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Now jokes aside. Unless you work towards a goal (eg new laptop at the end of the year), and you actively keep track of the extra savings it's very easy to blow the $4 saved per day on a whim, without even realizing. Your mindset changes to "I can buy drinks for my friends, I 've been saving this week it's cool", and you end up where you started. And that's fine, there is happiness to be had over buying your friends a drink.